Conventionally, an automotive fuel tank is typically mounted under the rear seats or under the mar floor, and is fixed against the lower surface of the vehicle body by steel straps passed longitudinally across the lower surface of the fuel tank. There have been attempts to favorably combine a fuel tank with a rear subframe. For instance, the subframe has a rectangular annular shape, and the fuel tank is received in an central recess defined by the rear subframe. In another case, the fuel tank is mounted on the upper surface of the rear subframe. In such cases, it would be possible to simplify and automate the assembly work by combining the fuel tank with the subframe into a sub assembly, and mounting this subassembly on the vehicle body.
However, the subassembly is typically mounted on the vehicle body with resilient bushings interposed therebetween to the end of preventing transmission of vibrations from the tires to the vehicle body and thereby improving the ride comfort of the vehicle, and the fuel tank is subjected to more severe vibrations and accelerations than it would be when it is mounted on the vehicle body. Therefore, special provisions have to be made when a fuel tank is to be mounted on the subframe. The special provisions include the increase in the rigidity of the fuel tank, the use of a relatively massive mounting structure, and so on which will ensure the integrity of the fuel tank, and keep the fuel tank securely fixed to the subframe under all conditions. Heretofore, it has been generally believed that the gains obtained from such a subassembly structure are not sufficient to justify the cost for such special provisions.